This proposal aims to significantly enhance existing electronic structure methods appropriate for modeling biological systems. Electronic structure methods permit the modeling of molecular systems from first principles without any experimental input or empiricism at very high computational cost. They find wide use in modeling small reaction regions as well as data generation for development of simpler empirical methods. There is strong demand to increase the size of treatable systems and reduce the time to solution for systems at the current limit of feasibility. The opportunity is to leverage the greatly increased power and greatly reduced cost of workstation/PC clusters as platforms for high-performance electronic structure calculations, together with fundamental improvements in the computational algorithms for second order Moller-Plesset theory, which yields accurate descriptions of covalent bonds, torsional potentials, hydrogen bonding and dispersion interactions in biological systems. The new computational formulation gives asymptotic linear scaling of computational cost with molecular size for the first time without discarding the small Van der Waals terms known to be important for hydrogen bonds, DMA base stacking, and other non-bonded interactions in biology.